export class Node {
  constructor(key) {
    this.key = key;
    this.left = undefined;
    this.right = undefined;
    this.x = undefined;
    this.y = undefined;
    this.level = undefined; //二叉树的层数
    this.leftTarget = undefined; //指向左子节点
    this.rightRarget = undefined; //指向右子节点
  }
  toString() {
    return `${this.key}`;
  }
}
